1. Field of the Invention
This invention relates to a low-alloy zinc material. More especially, this invention relates to a zinc alloy containing a minor amount of titanium. This invention is especially directed to a zinc alloy which has good wear and abrasion resistance, embossability, and strength and is suitable for manufacture into coins, coin blanks, and the like. This invention is directed to such a zinc alloy material which, furthermore, has good strength and good resistance to corrosion and tarnishing.
2. Discussion of the Prior Art
For the production of medals, plaques, decorative objects and the like, good cold forming qualities are required in addition to resistance to corrosion and tarnishing. In addition, the possibility must be provided for the performance of a variety of surface treatments.
Low-alloy zinc materials are known in a great variety (cf., for example, OE-PS 241,833, CH-PS 437,820). Attempts have been made to influence various properties of the basic material by the addition of alloying elements, and especially to increase the hardness and strength substantially above those of unalloyed zinc. These efforts have to some extent been quite successful, although the improvement of the one property has often been obtained at the cost of an impairment of the other. For example, a desirable great increase of the strength has often resulted in an appreciable lessening of resistance to corrosion.
For a long time, considerable efforts have been undertaken for the purpose of replacing the formerly common coin materials with other materials. Whereas in the case of the conventional coin materials, especially silver alloys, the value of the metal constituted a considerable part of the value of the coin, even exceeding it in some cases, the value of the metal in modern coins is of entirely secondary importance. Instead, increasing importance is being attached to the need for practical and uniform qualities in the coins that are to be made from the metal. For example, they must not corrode under a wide variety of conditions, they must retain their original color, and they must be resistant to wear and abrasion. Furthermore, since coin-operated machines are growing in popularity, increasing attention is being focused on the suitability of coins for use in such equipment. It must be assured that the coin material can be adapted to the advanced testing methods designed to preclude the cheating of coin-operated equipment. These and a number of other aspects are involved in the choice of a suitable material for making coins.
When a metal is to be used as a material for the production of medals, plaques and jewelry, the following considerations are important. For such articles, tin is often used as a material. This metal is comparatively expensive and is not the best choice in all cases as far as the desired characteristics are concerned. The problem thus exists of finding a material which will satisfy all of the above, sometimes conflicting, requirements, i.e., on which will have all of the above-mentioned qualtities simultaneously.